Structural basis for recognition of G-1-containing tRNA by histidyl-tRNA synthetase |
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| Authors: | Qingnan Tian Caiyan Wang Yuhuan Liu Wei Xie |
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| Affiliation: | 1Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou 510275, People''s Republic of China;2Center for Cellular & Structural biology, The Sun Yat-Sen University, 132 E. Circle Rd., University City, Guangzhou 510006, People''s Republic of China |
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| Abstract: | Aminoacyl-tRNA synthetases (aaRSs) play a crucial role in protein translation by linking tRNAs with cognate amino acids. Among all the tRNAs, only tRNAHis bears a guanine base at position -1 (G-1), and it serves as a major recognition element for histidyl-tRNA synthetase (HisRS). Despite strong interests in the histidylation mechanism, the tRNA recognition and aminoacylation details are not fully understood. We herein present the 2.55 Å crystal structure of HisRS complexed with tRNAHis, which reveals that G-1 recognition is principally nonspecific interactions on this base and is made possible by an enlarged binding pocket consisting of conserved glycines. The anticodon triplet makes additional specific contacts with the enzyme but the rest of the loop is flexible. Based on the crystallographic and biochemical studies, we inferred that the uniqueness of histidylation system originates from the enlarged binding pocket (for the extra base G-1) on HisRS absent in other aaRSs, and this structural complementarity between the 5′ extremity of tRNA and enzyme is probably a result of coevolution of both. |
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